Overview and Summary of the First Automotive CFD Prediction Workshop: DrivAer Model

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The First Automotive CFD Prediction Workshop was held in December 2019 at St Anne’s College at the University of Oxford with the aim to assess the ability of a broad range of computational fluid dynamics (CFD) methods to predict the flow over realistic automotive geometries. Here, results from 53 simulation data sets from 9 separate groups are analyzed for the open-source automotive DrivAer model (in the fastback and estate variants). The represented CFD approaches include Reynolds-averaged Navier-Stokes (RANS) approaches with a broad range of turbulence models, as well as scale-resolving approaches such as wall-modelled large-eddy simulation (WMLES) and hybrid RANS-LES methods (HRLM). A range of CFD codes was used, including commercial, academic, and open source. Compared to the two experimental data points, there was a large spread of CFD results. The difference between drag predictions among HRLM and RANS methods is significant, with an even larger mismatch for lift. The differences are found to be more significant for the estate geometry than for the fastback, with the former having larger areas of flow separation. In general it is found that the spread of HRLM is smaller than those for RANS approaches, with HRLM grouping closer to the range of experimental values. However, for HRLM, there is a systematic underprediction of the front lift coefficient that is irrespective of the mesh, turbulence model, and CFD code. Given that the majority of participants used the same mesh and boundary conditions, and in some cases the same CFD code, it suggests that also user choices around numerical schemes, convergence, and turbulence model coefficients may have a sizable impact, which was not possible to fully control in this first workshop. It is worth noting as well that the CFD simulations were conducted in a free-air environment and did not model the wind-tunnel geometry itself, which may also be an area requiring further study. The DrivAer model exhibits numerous complex flow physics, i.e., laminar/turbulent separation, diffusion of momentum in turbulent shear layers, and interactions of turbulent wakes with boundary layers. However, the nature of a community-driven workshop and the lack of extensive experimental data means that this article can only report the current state of the art and serve as a reference for future workshops and a springboard for more focused future studies where topics can be explored in greater detail.
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DOI
https://doi.org/10.4271/02-16-01-0005
Pages
30
Citation
Ashton, N., and van Noordt, W., "Overview and Summary of the First Automotive CFD Prediction Workshop: DrivAer Model," Commercial Vehicles 16(1):61-85, 2023, https://doi.org/10.4271/02-16-01-0005.
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Published
Aug 18, 2022
Product Code
02-16-01-0005
Content Type
Journal Article
Language
English